Controlling mark positions in documents

ABSTRACT

A document is represented as a node tree in a document processing system. Edits to a node are represented in a change record that has a one-way link to the node. A text mark has a one-way link to the change record. It deletes that link when the changes represented by the change record are reflected in the text mark. A memory management system releases the memory allocated to the change record when no other object links to it.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority of U.S.patent application Ser. No. 16/416,510, filed May 20, 2019, which isbased on and claims the benefit of U.S. provisional patent applicationSer. No. 62/842,688, filed May 3, 2019, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

Computer systems are currently in wide use. Some such systems includehost systems that host a service at a remote server location, for accessby client computing systems.

For example, one such system is a host computing system that hosts acontent creation service. The content creation service can allow clientcomputing systems to create and manage content. Some examples includehosted word processing services, spreadsheet services, documentmanagement services, slide presentation services, among a wide varietyof others.

These types of computing systems have a front end that exposes aninterface that can be accessed by client computing systems. In oneexample, the client computing systems communicate with the remote serverenvironment through a browser-based interface. For instance, it may bethat a user is using a client computing system to interact with a hostedword processing service, through a browser-based interface. The user caninvoke a content editing system on the client computing system to edit adocument that has been created and stored on the remote word processingservice.

In order to do that, the document can be represented to the contentediting system as a tree of connected nodes. The nodes are organizedinto a hierarchical tree and the job of the content editing system is tomodify the tree in response to user inputs. Nodes in the tree areorganized in a bidirectionally linked manner where a parent nodereferences its children nodes and all children reference their parentnode. Children can also be linked with one another as next and followingsiblings.

The tree can include, for instance, a root node that represents theentire document. Child nodes (or first level child nodes which dependdirectly from the root node) may represent sections in the document,paragraphs in the document, etc. Child nodes from the first level childnodes may represent items within each section or paragraph, such astext, an image, a table, etc.

In some areas, the content editing system needs to create and maintainreferences to specific positions in the content tree. Text processingsystems often deal with this by creating objects that behave aspersistent pointers into the content. These objects can be referred toas markup pointers, node locations, or text marks and will be referredto herein as a position mark, or as a text mark. A position mark canrefer to a position within the document or content by referring to anode in the node tree and then having an offset value which reflects thetracked position offset within the node that is to be tracked.

For example, when performing a text selection operation or a textinsertion operation, the position of the text that is selected or theposition where the text is to be inserted needs to be maintained. By wayof example, selection in a text document is performed by generating apair of position marks (references to positions in text). Thesepositions can be the start position and end position of the selectedtext. The span between the two positions is considered “selected” andcan be used as a target of editing operations (such as formatting,deleting, copying, etc.).

Another example of a use for a position mark is in pagination. Afterorganizing the content of a document into multiple pages, the contentediting system keeps references to beginnings and endings of each of thepages, which are again, represented as positions in the content tree.

In order to maintain their persistence during content modification,position marks are often implemented using doubly-linked structures.That is, a position mark object refers to a node in the content nodetree, and the node refers back to the position mark so that the positionmark can be corrected when the content near the position mark is deletedor modified.

The discussion above is merely provided for general backgroundinformation and is not intended to be used as an aid in determining thescope of the claimed subject matter.

SUMMARY

A document is represented as a node tree in a document processingsystem. Edits to a node are represented in a change record that has aone-way link to the node. A position mark has a one-way link to thechange record. It deletes that link when the changes represented by thechange record are reflected in the position mark. A memory managementsystem releases the memory allocated to the change record when no otherobject links to it.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter. The claimed subject matter is not limited to implementationsthat solve any or all disadvantages noted in the background.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of one example of a content tree.

FIG. 2 is a block diagram showing one example of a computing systemarchitecture.

FIG. 3 is a block diagram of one example of a change record.

FIG. 4 is a block diagram of one example of a node.

FIG. 5 is a block diagram of one example of a text mark.

FIGS. 6A-6C (collectively referred to herein as FIG. 6) show a flowdiagram illustrating one example of the operation of the architectureshown on FIG. 2.

FIGS. 7A-7H show examples of memory management.

FIG. 8 is a block diagram showing one example of the architecture shownin FIG. 1, deployed in a cloud computing architecture.

FIGS. 9-11 show examples of mobile devices that can be used in thearchitectures shown in the previous figures.

FIG. 12 is a block diagram showing one example of a computingenvironment that can be used in the architectures shown in the previousfigures.

DETAILED DESCRIPTION

As mentioned above, a position mark may be represented by a combinationof a reference to a node in the content tree and a character offsetwithin that node. However, when the content within the node is modified,then the position mark may become invalidated. For instance, if text isdeleted from the node, then the offset value may not be accurate. Thesame is true if the content in the node is moved, if insertions aremade, etc.

One way that this has been dealt with is to use the bidirectionallinking discussed above (e.g., attach the position mark to the node by astrong reference in which the position mark holds a reference to thenode to which it is attached, and the node also holds a reference backto the position mark that is attached to it). In those scenarios, when anode is modified, the position marks that are attached to the node arealso modified by logic within the node itself. This, of course, meansthat the node must have a reference back to all the position marks thatare attached to it. This can present problems.

For instance, where the content editing system no longer needs aposition mark, it may release that position mark by deleting itsreference to that position mark. In some computing systems, garbagecollection or other memory management systems will release memory whenthere is no reference to a particular object in memory. However, even ifthe content editing system deletes its reference to a position mark,that position mark will still have a reference to it, from the node itis attached to. The node will not know that the content editing systemhas released that position mark, and therefore it will not remove itsreference to that position mark. This will prevent the position markfrom being released within the memory corresponding to the node tree,which leads to a larger memory footprint for the node tree. This canlead to memory overrun situations or it can lead to an undesirably largememory footprint for the node tree.

FIG. 1 shows one example of a content tree 100 that represents adocument. Content tree 100 includes a set of nodes that are linked toone another. The nodes include root node 102, child nodes 104, 106 and108 (which are child nodes with root node 102 as their parent), andother child nodes 110-112 (which are children of node 104) and nodes 114and 116 (which are children of node 108). FIG. 1 also includes anexample of a portion 118 of an HTML representation 118 of the contenttree 100. The arrows 120, 122 and 124 represent position marks. Theposition marks 120 and 122, for instance, may represent content (e.g.,text) selection so that the span between position marks 120 and 122identifies the selected content. Position mark 124 may represent, forinstance, a bookmark or pagination mark. These are examples only.

It can be seen that when one of the nodes is changed, and that node isreferred to by a position mark, the position mark may become invalid. Byway of example, assume that position mark 120 is represented, in memory,as a node reference (which refers to node 112), and an offset referencewhich refers to the character offset within node 112 where the positionmark position is located. If some content in node 112 is deleted, thismay render the offset value in position mark 120 invalid.

In some current systems, in order to remedy this situation, node 112would include a reference back to position mark 120. When node 112 waschanged, the logic in node 112 would change position mark 120, whenneeded, in order to ensure that position mark 120 points to the properposition within node 112. However, this means that node 112 has areference back to position mark 120. This can be problematic, asdiscussed above, because when a content editing system releases itsreference to position mark 120 (because it is no longer needed) theobject in memory that represents position mark 120 will not be releasedbecause node 112 will still hold a reference to it.

The present description thus describes a system in which the nodes incontent tree 100 do not have references to position marks that areattached to them. Instead, the references only go one way. That is, eachof the position marks only has a reference in a direction toward itscorresponding node, but the node does not have a reference back to thoseposition marks. The position marks thus include logic to updatethemselves if the node they are attached to is changed. This isdescribed in greater detail below.

FIG. 2 is a block diagram of one example of a computing systemarchitecture 130 in which position marks can be used. Architecture 130illustratively includes content creation service computing system 132,and a plurality of different client computing systems 134-136 which canbe connected to content creation service computing system 132 throughnetwork 138. Thus, network 138 can be a local area network, a wide areanetwork, a cellular communication network, a near field communicationnetwork, or any of a wide variety of networks or combinations ofnetworks.

Content creation service computing system 132 illustratively includes aset of servers 140, a service front end system 142, a service back endsystem 144, data store 146 (which can store content 148 and other items150) and it can include other items 152. Service front end system 142exposes interfaces that can be accessed by client computing systems 134and 136 in order to create, modify and otherwise manage content 148,such as documents. In doing so, front end computing system 142 receivesinputs through the exposed interface and interacts with service back endsystem 144 which, itself, performs operational steps on content 148based on the inputs received by service front end system 142.

Client computing systems 134 and 136 are shown generating userinterfaces 154 and 156 for interaction by users 158 and 160,respectively. User 158 illustratively interacts with user interface 154in order to control and manipulate client computing system 134 and someportions of content creation service computing system 132. Similarly,user 160 can interact with user interfaces 156 in order to control andmanipulate client computing system 136 and some portions of contentcreation service computing system 132. Client computing systems 134 and136 may be similar or different. For purposes of the present discussion,it will be assumed that they are similar so that only client computingsystem 134 is described herein, in more detail. This is by way ofexample only.

Client computing system 134, in one example, includes one or moreprocessors 162, data store 164 (which can store content 166—which may bea representation of some content 148 or different content) and it caninclude other items 168. System 134 also illustratively includes browser170, and document processing system 171. System 171 can include contentediting system 172, memory management system 173, and editor memory 174which may be used by content editing system 172 during editing ofcontent 166. Editor memory 174 may include a content tree 176 thatrepresents the content being edited, and it can include other items 178.System 134 can include a wide variety of other client computing systemfunctionality 180.

It will be noted that content 148 and 166 can be stored in data stores146 and 164 as content trees. It can also be stored in a differentstructure. When the content is loaded into editor memory 174, it isloaded as a content tree 176. Content tree 176 can include the contentitself or a reference to a different structure that holds the content

In the example shown in FIG. 1, content editing system 172 can include awide variety of different types of editing functionality. For instance,system 172 can include selection functionality 182 that allows system172 to select portions of content represented by content tree 176 forediting. System172 can include bookmark functionality 184 which allowssystem 172 to maintain a bookmark within the content tree 176. System172 can include pagination functionality 186 that allows system 172 toidentify page breaks in the content represented by content tree 176.System 172 can include highlight functionality 188 which allows system172 to perform highlights in the content being edited, and it can ofcourse include a wide variety of other editing functionality 190 thatallows system 172 to perform a wide variety of other editing functions,such as content move functions, delete functions, copy and pastefunctions, etc.

In order to edit a document (which may be stored as content 148 oncomputing system 132), client computing system 134 illustratively allowsuser 158 to invoke content editing system 172 which edits the content,based on user inputs, through a browser-based interface using browser170. Content editing system 172 first downloads the content to be editedand loads a corresponding content tree 176, representing that content,into editor memory 174. It then edits the content tree 176 based on userinputs from user 158 through user interfaces 154. In performing thoseediting operations, content editing system 172 may use position marks.Memory management system 173 illustratively manages editor memory 174.Therefore, system 173 allocates memory for content tree 176 (and as willbe described below, change records and position marks). It also releasesthat memory when objects are no longer referred to by other objects ineditor memory 174. This is all described in greater detail below.

Before describing the use of position marks in more detail, a briefdescription of some of the items in content tree 176 will first bedescribed.

FIG. 3 is a block diagram of one example of a change record 202 that canbe created as an object in memory 174 by a node (such as node 112 shownin FIG. 1) when content editing system 172 changes the information innode 112 using an edit operation. FIG. 3 shows that change record 202can include change information 204, node/change record reference 206,and it can include other items 208. Change information 204 representsthe information that was changed by content editing system 172 in thenode (e.g., node 112) which created change record 202. Node/changerecord reference 206 is a reference to either node 112, or to asubsequent change record that will be generated based on subsequentchanges to node 112 by content editing system 172. Change record 202 caninclude other items 208. Thus, once created, change record 202represents changes made to node 112 by content editing system 172 and itincludes a one-way reference or link to the node 112 that created it.

FIG. 4 shows one example of a node, such as node 112, in the contenttree 100 shown in FIG. 1. Node 112 is illustratively an object in memory174 that includes content data that the node represents and logic thatis executed under certain circumstances, such as when a change is madeto the content in the node. In another example, the nodes share some orall logic across nodes. In yet another example, the nodes do not holdthe content, but hold references into another structure that holds thecontent. In the example shown in FIG. 4, node 112 includes last changerecord reference 192, change record generator 193, reference updatesystem 194 and it can include other node data and functionality 196(which can include the content represented by the node).

The last change record reference 192 is a reference to a most recentchange record that reflects changes to node 112 most recently made bycontent editing system 172. One example of a change record is describedin more detail above with respect to FIG. 3. Reference update system 194illustratively includes node update logic 198 and change record updatelogic 200. Change record generator 193 generates a change record thatrepresents the changed data. Node update logic 198 updates the lastchange record reference 192 so that it refers to the newly createdchange record. Change record update logic 200 modifies the reference inthe change record so that it points to the newly created change record,instead of to node 112.

FIG. 5 shows an example of a position mark (such as position mark 120shown in FIG. 1). Position mark 120 is illustratively an object inmemory 174 that includes a reference to another object in memory andlogic that is executed under certain circumstances. As with nodes,position marks can include their own logic or share logic across otherobjects. In the example shown in FIG. 5, position mark 120 includesnode/change record reference 210, new change record detector 212, changerecord traversal logic 214, change interpretation logic 216, referenceupdate logic 218, offset update logic 220, and it can include a widevariety of other position mark data and functionality 222. Node/changerecord reference 210 refers to node 112, or any intervening changerecords 202 that have been generated by node 112 and to which positionmark 120 refers. Reference 210 can also include an offset valueindicative of an offset within the node it refers to, to identify aspecific position in the content represented by tree 100.

New change record detector 212 detects when a new change record 202 hasbeen generated by node 112. For instance, it can detect that thenode/change record reference 206 in change record 202 has been updatedto point to a new change record, instead of to node 112. It can detect anew change record in other ways as well.

Change record traversal logic 214 illustratively traverses thereferences from the change record to which position mark 120 refers, upthrough all intervening change records to node 112. Changeinterpretation logic 216 interprets the change information 204 in eachof the change records that are traversed to identify an overall changevalue that represents the overall changes that have been made to node112, and that are represented by the traversed change records.

Reference update logic 218 then updates node/change record reference 210so that it refers to the most recent change record. Offset update logic220 modifies the offset value in position mark 120 based upon thechanges reflected in the various change records traversed by changerecord traversal logic 214.

FIGS. 6A-6C (collectively referred to herein as FIG. 6) show a flowdiagram illustrating one example of the operation of content editingsystem 172, memory management system 173, and content tree 176 inmaintaining and managing position marks. It is first assumed that someitem of content 148 has been generated and stored in hosted contentcreation computing system 132. The item of content can be a wordprocessing document, a spreadsheet document, a slide presentationdocument, or another item of content. This is indicated by block 230 inthe flow diagram of FIG. 6. Next, it is assumed that user 158 hasinteracted with interfaces 154 in order to launch or invoke contentediting system 172 to edit content 148. In doing so, the content 148that is being edited can be downloaded into data store 164, or thecontent tree 176 corresponding to the content to be edited can bedownloaded to client computing system 134, and stored, by memorymanagement system 173, in editor memory 174. The editor memory 174 maybe part of content editing system 172 or separate therefrom. Contentediting system 122 and memory management system 173 illustratively use abrowser-based interface implemented by browser 170, in order to interactwith content tree 176 and content creation service computing system 132.Launching or invoking content editing system 172 is indicated by block232 in the flow diagram of FIG. 6. Loading the content tree into theclient computing system memory 174 is indicated by block 234.

As discussed above, the content tree 176 can include nodes which arerepresented by block 236 in the flow diagram of FIG. 6. The nodes canhave links or references to other nodes in a parent/child relationship,or a sibling relationship. This is indicated by block 238. The contenttree can include other items 240 as well.

At some point, a component of content editing system 172 creates aposition mark and holds a reference to that position mark. The positionmark, itself, refers to a node in the content tree and it also includesan offset, within the node, identifying a particular position in thenode, and thus in the document represented by tree 100. This isindicated by block 242 in the flow diagram of FIG. 6.

FIGS. 7A-7G show a sequence of diagrams that will be discussed inconjunction with FIGS. 2-6. FIG. 7A shows an example in which node 112(of content tree 100), is shown. FIG. 7A also shows that a component ofcontent editing system 172 has generated a position mark (e.g., positionmark 120) which holds a reference to node 112, the reference beingindicated by arrow 244. It is assumed, for the sake of example, that theselection functionality 182 in content editing system 172 holds areference to position mark 120, for the purpose of performing contentselection. The reference is indicated by arrow 246 in FIG. 7A.

Next, it is assumed that user 158 interacts with interfaces 154 causingcontent editing system 172 to change information in node 112. This isindicated by block 248 in the flow diagram of FIG. 6. The changes can beany changes, such as copy and paste, selection, moving text, deletinginformation, adding information, modifying information, etc.

In response to that change, the change record generator 193 in node 112generates a change record to reflect the changed information. The changerecord is identified at 250 in FIG. 7B. Change record update logic 200in node 112 then updates change record 250 to add a reference in changerecord 250 to node 112. This is indicated by arrow 252 in the flowdiagram of FIG. 7B. Node update logic 198 then updates the node 112,itself, so that the last change record reference 192 now holds areference to change record 250. This is indicated by arrow 254 in FIG.7B. Generating the first change record 250 that reflects the change, andholding the reference 254 to that change record, is indicated by block256 in the flow diagram of FIG. 6. Having node 112 configure the changerecord 250 so that it holds a reference 252 to node 112 is indicated byblock 258.

New change record detector 212 detects that node 112 has created changerecord 250. Reference update logic 218 then updates the node/changerecord reference 210 (in position mark 120) so that it now refers to thechange record 250, instead of to node 112. This is indicated by block260 in the flow diagram of FIG. 6, and this reference is indicated byarrow 262 in FIG. 7B.

It may be that, at some point, content editing system 172 makes anotherchange to node 112, subsequent to the change reflected in change record250. This is indicated by block 264 in the flow diagram of FIG. 6. Atthat point, change record generator 193 generates a subsequent changerecord to reflect the newly made changes by content editing system 172.Node update logic 198 then updates the change record reference 192 innode 112 so that it now refers to the subsequent change record (or mostrecent change record) just generated by node 112. This is indicated byblock 266 in the flow diagram of FIG. 6.

Change record update logic 200 configures the newly created changerecord so that it includes a reference back to node 112. It alsoconfigures the previous change record 250 so that it now contains areference to the subsequent change record, instead of to the node 112,itself. The results of this are shown in FIG. 7C.

FIG. 7C is similar to FIG. 7B, except it now shows that node 112 hascreated a new (or subsequent) change record 268. FIG. 7C shows thatchange record 250 now has a reference 270 to the newly created changerecord 268, instead of to node 112. It also shows that change record 268has a reference 272 to node 112, and that node 112 now has a reference274 to change record 268, instead of to change record 250. Having thenode 112 configure change record 250 so that its reference 270 nowpoints to change record 268 is shown at block 276 in the flow diagram ofFIG. 6. Having node 112 configure the newly created change record 268,and configuring change record 268 so that it refers (by arrow 272) tonode 112 is also indicated by block 276.

Reference update system 194 then deletes the reference in node 112 tochange record 250. This is indicated by block 278 in the flow diagram ofFIG. 6. New change record detector 212 in position mark 120 detectscreation of the subsequent change record 268. This is indicated by block280 in the flow diagram of FIG. 6. Also, for the sake of example, it isassumed that a component of content editing system 172 creates a newposition mark 282 with a reference to change record 268. Thus, contentediting system 172 also holds a reference 284 (shown in FIG. 7C) to thenew position mark 282. Creating the new position mark is indicated byblock 286 in the flow diagram of FIG. 6.

At this point, it can be seen that content editing system 172 holdsreferences to two position marks (reference 246 to position mark 120 andreference 284 to position mark 282). Position mark 120 holds a reference262 to change record 250 while position mark 282 holds a reference 288to change record 268.

FIG. 7D is similar to FIG. 7C, except that it shows that node 112 hasnow generated two additional change records 292 and 294, but theposition marks 120 and 282 have not updated themselves yet. Thereference in change record 268 has been changed to reference 296, whichnow refers to change record 292. Change record 292 also has a reference298 that refers to change record 294. Change record 294, in turn, has areference 300 that refers to node 112, and node 112 has a reference 302that now refers to change record 294.

Change record traversal logic 214, in position mark 120, will traversethe references 262, 270, 296 and 298 through change records 250, 268,292 and 294 up to node 112, and, in doing so, change interpretationlogic 216 will interpret the changes to node 112 that are reflected ineach of those change records 250, 268, 292 and 294. Traversing thechange records in this way is indicated by block 290 in the flow diagramof FIG. 6.

Position mark 120 then updates itself based upon the changes interpretedfrom all of the change records 250, 268, 292 and 294. For example,position mark 120 can update the offset value that it holds relative tonode 112. It can update other information as well. This is indicated byblock 306 in the flow diagram of FIG. 6.

Reference update logic 218 then updates the node/change record reference210 in position mark 120 so that it now points to change record 294.This reference or link is indicated by the dashed arrow 308 in FIG. 7D,and the process of updating the reference to change record 294 isindicated by block 310 in the flow diagram of FIG. 6.

Reference update logic 218 then deletes its reference to any or allother change records. For instance, it deletes its reference 262 tochange record 250. Deleting the reference to the old change record isindicated by block 312 in the flow diagram of FIG. 6.

This results in the structure shown in FIG. 7E. It can now be seen thatchange record 250 has nothing that refers to it. Similarly, FIG. 7Eshows that position mark 282 has similarly traversed links 296 and 298and change records 268, 292, and 294 and updated itself and its ownreference so that position mark 282 now contains a reference 314 tochange record 294. In that case, reference 288 can be removed to yieldthe structure shown in FIG. 7F. Because change record 250 now hasnothing that refers to it, memory management system 173 illustrativelyreleases it from memory 174. For example, it can be collected by agarbage collection or other memory maintenance mechanism. Once it isremoved, then change record 268 has nothing referring to it. Changerecord 268 can thus be released from memory as well. Once change record268 is released, then change record 292 has nothing referring to it, andit can be released as well.

Next, assume that content editing system 172 no longer needs positionmark 282. In that case, system 172 deletes its own reference 284 toposition mark 282 yielding the structure illustrated in FIG. 7G. Now,because position mark 282 has nothing referring to it, it can bereleased in memory and collected by a garbage collector or other memorymaintenance system. This yields the structure shown in FIG. 7H. Oncecontent editing system 172 no longer needs position mark 120, it deletesits own reference 246 to position mark 120. In that case, position mark120 can be released from memory.

Releasing all change records and position marks that are not referred tois indicated by block 316 in the flow diagram of FIG. 6. Collecting themand releasing them using a garbage collection mechanism is indicated byblock 318. They can be released in other ways as well, and this isindicated by block 320.

It should also be noted that the present discussion can be applied in acollaborative environment. For instance, assume that users 158 and 160are collaborating on an item of content 148 through content creationservice computing system 132. In that case, the changes input by user158 through content editing system 172 are propagated to clientcomputing system 136 through service computing system 132 and network138. Each content editing system 172 (in each client computing system)then keeps an object representing the changes and the client computingsystem they came from, as well as the position of the content editingsystem 172 in content 148, on its own client computing system 134. Thus,as the content editing system in client computing system 136 generatesposition marks, those position marks are maintained, in the objectrepresenting the content editing system 172 in client computing system136, on client computing system 134. The same is done with changes sentby client computing system 136. In this way, content editing system 172and the code in content tree 176 (e.g., the code in the nodes, changerecords and position marks) can be maintained, up-to-date, to reflectthe changes made by user 160 as well. The changes are processed in thesame way as if they were locally made, but an identifier is maintainedto identify where the changes came from (e.g., the client computingsystem they came from). Memory management system 173 can thus manageeditor memory 174 based not only on the changes made by content editingsystem 172, but by those made by the content editing system in clientcomputing system 136, where collaboration is involved.

It can thus be seen that the present description enables memorymanagement system 173 to maintain a much smaller footprint for contenttree 176 than would otherwise be the case. As soon as a position mark orchange record is no longer referred to by another object, memorymanagement system 173 releases that memory for other usage. This reducesmemory overrun issues and maintains a smaller memory footprint. It alsomakes the nodes in content tree 176 computationally independent of thenumber of position marks that refer to them. Change record generator193, and reference update system 194, which are used to generate changerecords and modify the references in the node itself, and the in thenewly created and last created change record, deal only with a constantsize reference between the node, the last change record, and oneprevious change record (because the logic changes the reference in theprevious change record to refer to the last change record). It does notneed to deal with updating an entire collection of position marks whichmay be attached to the node. In fact, the node does not even need toknow that any position marks are attached to it. Further, even thoughthe total number of position mark modifications is generallyproportional to the multiple of change records and position marks thatare being used, the overall computational distribution benefits are seenat the innermost data processing levels of content tree modification.That is, the maintenance of the position marks is performed at themoment when the position marks are used. This often happens relativelyinfrequently relative to node changes. Thus, the present descriptionsaves on computational overhead as well.

It will be noted that the above discussion has described a variety ofdifferent systems, components and/or logic. It will be appreciated thatsuch systems, components and/or logic can be comprised of hardware items(such as processors and associated memory, or other processingcomponents, some of which are described below) that perform thefunctions associated with those systems, components and/or logic. Inaddition, the systems, components and/or logic can be comprised ofsoftware that is loaded into a memory and is subsequently executed by aprocessor or server, or other computing component, as described below.The systems, components and/or logic can also be comprised of differentcombinations of hardware, software, firmware, etc., some examples ofwhich are described below. These are only some examples of differentstructures that can be used to form the systems, components and/or logicdescribed above. Other structures can be used as well.

The present discussion has mentioned processors and servers. In oneexample, the processors and servers include computer processors withassociated memory and timing circuitry, not separately shown. They arefunctional parts of the systems or devices to which they belong and areactivated by, and facilitate the functionality of the other componentsor items in those systems.

Also, a number of user interface displays have been discussed. They cantake a wide variety of different forms and can have a wide variety ofdifferent user actuatable input mechanisms disposed thereon. Forinstance, the user actuatable input mechanisms can be text boxes, checkboxes, icons, links, drop-down menus, search boxes, etc. They can alsobe actuated in a wide variety of different ways. For instance, they canbe actuated using a point and click device (such as a track ball ormouse). They can be actuated using hardware buttons, switches, ajoystick or keyboard, thumb switches or thumb pads, etc. They can alsobe actuated using a virtual keyboard or other virtual actuators. Inaddition, where the screen on which they are displayed is a touchsensitive screen, they can be actuated using touch gestures. Also, wherethe device that displays them has speech recognition components, theycan be actuated using speech commands

A number of data stores have also been discussed. It will be noted theycan each be broken into multiple data stores. All can be local to thesystems accessing them, all can be remote, or some can be local whileothers are remote. All of these configurations are contemplated herein.

Also, the figures show a number of blocks with functionality ascribed toeach block. It will be noted that fewer blocks can be used so thefunctionality is performed by fewer components. Also, more blocks can beused with the functionality distributed among more components.

FIG. 8 is a block diagram of architecture 130, shown in FIG. 2, exceptthat its elements are disposed in a cloud computing architecture 500.Cloud computing provides computation, software, data access, and storageservices that do not require end-user knowledge of the physical locationor configuration of the system that delivers the services. In variousembodiments, cloud computing delivers the services over a wide areanetwork, such as the internet, using appropriate protocols. Forinstance, cloud computing providers deliver applications over a widearea network and they can be accessed through a web browser or any othercomputing component. Software or components of architecture 130 as wellas the corresponding data, can be stored on servers at a remotelocation. The computing resources in a cloud computing environment canbe consolidated at a remote data center location or they can bedispersed. Cloud computing infrastructures can deliver services throughshared data centers, even though they appear as a single point of accessfor the user. Thus, the components and functions described herein can beprovided from a service provider at a remote location using a cloudcomputing architecture. Alternatively, they can be provided from aconventional server, or they can be installed on client devicesdirectly, or in other ways.

The description is intended to include both public cloud computing andprivate cloud computing. Cloud computing (both public and private)provides substantially seamless pooling of resources, as well as areduced need to manage and configure underlying hardware infrastructure.

A public cloud is managed by a vendor and typically supports multipleconsumers using the same infrastructure. Also, a public cloud, asopposed to a private cloud, can free up the end users from managing thehardware. A private cloud may be managed by the organization itself andthe infrastructure is typically not shared with other organizations. Theorganization still maintains the hardware to some extent, such asinstallations and repairs, etc.

In the example shown in FIG. 8, some items are similar to those shown inFIG. 2 and they are similarly numbered. FIG. 8 specifically shows thatcomputing system 132 can be located in cloud 502 (which can be public,private, or a combination where portions are public while others areprivate). Therefore, users 158 and 160 use client computing systems 134and 136, respectively, to access those systems through cloud 502.

FIG. 8 also depicts another example of a cloud architecture. FIG. 8shows that it is also contemplated that some elements of computingsystem 132 can be disposed in cloud 502 while others are not. By way ofexample, data store 148 can be disposed outside of cloud 502, andaccessed through cloud 502. Regardless of where they are located, theycan be accessed directly by systems 134 and 136, through a network(either a wide area network or a local area network), they can be hostedat a remote site by a service, or they can be provided as a servicethrough a cloud or accessed by a connection service that resides in thecloud. All of these architectures are contemplated herein.

Similarly, FIG. 8 shows that some or all of client computing systems 134and 136 (or other client computing systems) can be deployed as virtualclient computing systems 504 in cloud 502 or in a different cloud. Userscan access the virtual client(s) 504 through any of a variety ofdifferent user devices.

It will also be noted that architecture 130, or portions of it, can bedisposed on a wide variety of different devices. Some of those devicesinclude servers, desktop computers, laptop computers, tablet computers,or other mobile devices, such as palm top computers, cell phones, smartphones, multimedia players, personal digital assistants, etc.

FIG. 9 is a simplified block diagram of one illustrative example of ahandheld or mobile computing device that can be used as a user's orclient's hand held device 16, in which the present system (or parts ofit) can be deployed. FIGS. 10-11 are examples of handheld or mobiledevices.

FIG. 9 provides a general block diagram of the components of a clientdevice (or user device) 16 that can run components computing system 132or client systems 134 and 136 that interacts with architecture 130, orboth. In the device 16, a communications link 13 is provided that allowsthe handheld device to communicate with other computing devices andunder some embodiments provides a channel for receiving informationautomatically, such as by scanning Examples of communications link 13include an infrared port, a serial/USB port, a cable network port suchas an Ethernet port, and a wireless network port allowing communicationthough one or more communication protocols including General PacketRadio Service (GPRS), LTE, HSPA, HSPA+ and other 3G and 4G radioprotocols, 1Xrtt, and Short Message Service, which are wireless servicesused to provide cellular access to a network, as well as Wi-Fiprotocols, and Bluetooth protocol, which provide local wirelessconnections to networks.

In other examples, applications or systems are received on a removableSecure Digital (SD) card that is connected to a SD card interface 15. SDcard interface 15 and communication links 13 communicate with aprocessor 17 (which can also embody processors or servers from otherFIGS.) along a bus 19 that is also connected to memory 21 andinput/output (I/O) components 23, as well as clock 25 and locationsystem 27.

I/O components 23, in one example, are provided to facilitate input andoutput operations. I/O components 23 for various examples of the device16 can include input components such as buttons, touch sensors,multi-touch sensors, optical or video sensors, voice sensors, touchscreens, proximity sensors, microphones, tilt sensors, and gravityswitches and output components such as a display device, a speaker, andor a printer port. Other I/O components 23 can be used as well.

Clock 25 illustratively comprises a real time clock component thatoutputs a time and date. It can also, illustratively, provide timingfunctions for processor 17.

Location system 27 illustratively includes a component that outputs acurrent geographical location of device 16. This can include, forinstance, a global positioning system (GPS) receiver, a LORAN system, adead reckoning system, a cellular triangulation system, or otherpositioning system. It can also include, for example, mapping softwareor navigation software that generates desired maps, navigation routesand other geographic functions.

Memory 21 stores operating system 29, network settings 31, applications33, application configuration settings 35, data store 37, communicationdrivers 39, and communication configuration settings 41. Memory 21 caninclude all types of tangible volatile and non-volatilecomputer-readable memory devices. It can also include computer storagemedia (described below). Memory 21 stores computer readable instructionsthat, when executed by processor 17, cause the processor to performcomputer-implemented steps or functions according to the instructions.Similarly, device 16 can have a client system 24 which can run variousapplications or embody parts or all of architecture 130. Processor 17can be activated by other components to facilitate their functionalityas well.

Examples of the network settings 31 include things such as proxyinformation, Internet connection information, and mappings. Applicationconfiguration settings 35 include settings that tailor the applicationfor a specific enterprise or user. Communication configuration settings41 provide parameters for communicating with other computers and includeitems such as GPRS parameters, SMS parameters, connection user names andpasswords.

Applications 33 can be applications that have previously been stored onthe device 16 or applications that are installed during use, althoughthese can be part of operating system 29, or hosted external to device16, as well.

FIG. 10 shows one example in which device 16 is a tablet computer 600.In FIG. 10, computer 600 is shown with user interface display screen602. Screen 602 can be a touch screen (so touch gestures from a user'sfinger can be used to interact with the application) or a pen-enabledinterface that receives inputs from a pen or stylus. It can also use anon-screen virtual keyboard. Of course, it might also be attached to akeyboard or other user input device through a suitable attachmentmechanism, such as a wireless link or USB port, for instance. Computer600 can also illustratively receive voice inputs as well.

FIG. 11 shows that the device can be a smart phone 71. Smart phone 71has a touch sensitive display 73 that displays icons or tiles or otheruser input mechanisms 75. Mechanisms 75 can be used by a user to runapplications, make calls, perform data transfer operations, etc. Ingeneral, smart phone 71 is built on a mobile operating system and offersmore advanced computing capability and connectivity than a featurephone.

Note that other forms of the devices 16 are possible.

FIG. 12 is one example of a computing environment in which architecture130, or parts of it, (for example) can be deployed. With reference toFIG. 12, an example system for implementing some embodiments includes acomputing device in the form of a computer 810. Components of computer810 may include, but are not limited to, a processing unit 820 (whichcan comprise processors or servers from previous FIGS.), a system memory830, and a system bus 821 that couples various system componentsincluding the system memory to the processing unit 820. The system bus821 may be any of several types of bus structures including a memory busor memory controller, a peripheral bus, and a local bus using any of avariety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus. Memory andprograms described with respect to FIG. 2 can be deployed incorresponding portions of FIG. 12.

Computer 810 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 810 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media is different from, anddoes not include, a modulated data signal or carrier wave. It includeshardware storage media including both volatile and nonvolatile,removable and non-removable media implemented in any method ortechnology for storage of information such as computer readableinstructions, data structures, program modules or other data. Computerstorage media includes, but is not limited to, RAM, ROM, EEPROM, flashmemory or other memory technology, CD-ROM, digital versatile disks (DVD)or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by computer 810. Communication media typically embodiescomputer readable instructions, data structures, program modules orother data in a transport mechanism and includes any informationdelivery media. The term “modulated data signal” means a signal that hasone or more of its characteristics set or changed in such a manner as toencode information in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of any of the aboveshould also be included within the scope of computer readable media.

The system memory 830 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 831and random access memory (RAM) 832. A basic input/output system 833(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 810, such as during start-up, istypically stored in ROM 831. RAM 832 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 820. By way of example, and notlimitation, FIG. 12 illustrates operating system 834, applicationprograms 835, other program modules 836, and program data 837.

The computer 810 may also include other removable/non-removablevolatile/nonvolatile computer storage media. By way of example only,FIG. 12 illustrates a hard disk drive 841 that reads from or writes tonon-removable, nonvolatile magnetic media, and an optical disk drive 855that reads from or writes to a removable, nonvolatile optical disk 856such as a CD ROM or other optical media. Other removable/non-removable,volatile/nonvolatile computer storage media that can be used in theexemplary operating environment include, but are not limited to,magnetic tape cassettes, flash memory cards, digital versatile disks,digital video tape, solid state RAM, solid state ROM, and the like. Thehard disk drive 841 is typically connected to the system bus 821 througha non-removable memory interface such as interface 840, and optical diskdrive 855 are typically connected to the system bus 821 by a removablememory interface, such as interface 850.

Alternatively, or in addition, the functionality described herein can beperformed, at least in part, by one or more hardware logic components.For example, and without limitation, illustrative types of hardwarelogic components that can be used include Field-programmable Gate Arrays(FPGAs), Program-specific Integrated Circuits (ASICs), Program-specificStandard Products (ASSPs), System-on-a-chip systems (SOCs), ComplexProgrammable Logic Devices (CPLDs), etc.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 12, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 810. In FIG. 12, for example, hard disk drive 841 isillustrated as storing operating system 844, application programs 845,other program modules 846, and program data 847. Note that thesecomponents can either be the same as or different from operating system834, application programs 835, other program modules 836, and programdata 837. Operating system 844, application programs 845, other programmodules 846, and program data 847 are given different numbers here toillustrate that, at a minimum, they are different copies.

A user may enter commands and information into the computer 810 throughinput devices such as a keyboard 862, a microphone 863, and a pointingdevice 861, such as a mouse, trackball or touch pad. Other input devices(not shown) may include a joystick, game pad, satellite dish, scanner,or the like. These and other input devices are often connected to theprocessing unit 820 through a user input interface 860 that is coupledto the system bus, but may be connected by other interface and busstructures, such as a parallel port, game port or a universal serial bus(USB). A visual display 891 or other type of display device is alsoconnected to the system bus 821 via an interface, such as a videointerface 890. In addition to the monitor, computers may also includeother peripheral output devices such as speakers 897 and printer 896,which may be connected through an output peripheral interface 895.

The computer 810 is operated in a networked environment using logicalconnections to one or more remote computers, such as a remote computer880. The remote computer 880 may be a personal computer, a hand-helddevice, a server, a router, a network PC, a peer device or other commonnetwork node, and typically includes many or all of the elementsdescribed above relative to the computer 810. The logical connectionsdepicted in FIG. 12 include a local area network (LAN) 871 and a widearea network (WAN) 873, but may also include other networks. Suchnetworking environments are commonplace in offices, enterprise-widecomputer networks, intranets and the Internet.

When used in a LAN networking environment, the computer 810 is connectedto the LAN 871 through a network interface or adapter 870. When used ina WAN networking environment, the computer 810 typically includes amodem 872 or other means for establishing communications over the WAN873, such as the Internet. The modem 872, which may be internal orexternal, may be connected to the system bus 821 via the user inputinterface 860, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 810, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 12 illustrates remoteapplication programs 885 as residing on remote computer 880. It will beappreciated that the network connections shown are exemplary and othermeans of establishing a communications link between the computers may beused.

It should also be noted that the different embodiments described hereincan be combined in different ways. That is, parts of one or moreembodiments can be combined with parts of one or more other embodiments.All of this is contemplated herein.

Example 1 is a document processing system, comprising:

a content tree generator that generates a content tree that represents acontent document and has a node;

a content editing system that makes a modification to the node, the nodeincluding:

a change record generator that generates a first change recordrepresenting the modification to the node; and

a reference update system that updates a reference in the first changerecord to refer to the node and that updates a reference in the node torefer to the first change record; and

a text mark that has a one-way reference to the node, and a positionvalue indicative of a position in the node, and text mark referenceupdate logic that updates the one-way reference to the node to be aone-way reference to the first change record after the first changerecord is generated.

Example 2 is the document processing system of any or all previousexamples wherein the content editing system is configured to make asubsequent modification to the node and wherein the change recordgenerator is configured to generate a subsequent change recordrepresenting the subsequent modification to the node.

Example 3 is the document processing system of any or all previousexamples wherein the reference update system in the node is configuredto generate a reference in the subsequent change record to the node,update the reference in the first change record to be a one-wayreference to the subsequent change record and then to delete thereference, in the node, to the first change record and generate areference, in the node, to the subsequent change record.

Example 4 is the document processing system of any or all previousexamples wherein the text mark comprises:

a new change record detector configured to detect generation of thesubsequent change record, wherein the text mark reference update logicin the text mark is configured to update the one-way reference to thefirst change record to be a one-way reference to the subsequent changerecord.

Example 5 is the document processing system of any or all previousexamples wherein the text mark comprises:

change record traversal logic configured to traverse the first changerecord and the subsequent change record using the one-way reference, inthe text mark, to the first change record, the one-way reference, in thefirst change record, to the subsequent change record, and the reference,in the subsequent change record, to the node.

Example 6 is the document processing system of any or all previousexamples wherein the text mark comprises:

change interpretation logic configured to identify the modification andsubsequent modification based on traversal of the first change recordand the subsequent change record and generate a change interpretationbased on the identified modification and subsequent modification.

Example 7 is the document processing system of any or all previousexamples wherein the text mark comprises:

offset update logic configured to update the position value in the textmark, identifying the position in the node, based on the changeinterpretation.

Example 8 is the document processing system of any or all previousexamples wherein the text mark reference update logic is configured toupdate the one-way reference to the first change record, in the textmark, to be a one-way reference to the node.

Example 9 is the document processing system of any or all previousexamples and further comprising:

a memory management system that allocates memory for the text mark, thenode, the first change record and the subsequent change record and thatreleases memory allocated to any change record which is not referred toby any text mark, change record, or node.

Example 10 is the document processing system of any or all previousexamples wherein the content editing system comprises:

a browser-based interface that receives edit user inputs and edits thecontent document based on the edit user inputs.

Example 11 is a method of processing a content document, comprising:

receiving a content tree that represents the content document and has anode;

making a modification to the node;

using a change record generator in the node to generate a first changerecord representing the modification to the node; and

using a reference update system in the node to update a reference in thefirst change record to refer to the node and that update a reference inthe node to refer to the first change record; and

updating a text mark, that has a one-way reference to the node, and aposition value indicative of a position in the node, by changing theone-way reference to the node to be a one-way reference to the firstchange record.

Example 12 is the method of any or all previous examples and furthercomprising:

making a subsequent modification to the node; and

generating a subsequent change record representing the subsequentmodification to the node.

Example 13 is the method of any or all previous examples and furthercomprising, using the reference update system in the node to performsteps of:

generating a reference in the subsequent change record to the node;

updating the reference in the first change record to be a one-wayreference to the subsequent change record;

deleting the reference, in the node, to the first change record; and

generating a reference, in the node, to the subsequent change record.

Example 14 is the method of any or all previous examples and furthercomprising:

detecting, with the text mark, generation of the subsequent changerecord; and

updating the one-way reference to the first change record to be aone-way reference to the subsequent change record.

Example 15 is the method of any or all previous examples and furthercomprising:

traversing, with change record traversal logic in the text mark, thefirst change record and the subsequent change record using the one-wayreference, in the text mark, to the first change record, the one-wayreference, in the first change record, to the subsequent change record,and the reference, in the subsequent change record, to the node;

identifying, with change interpretation logic in the text mark, themodification and subsequent modification based on traversal of the firstchange record and the subsequent change record; and

generating a change interpretation based on the identified modificationand subsequent modification.

Example 16 is the method of any or all previous examples and furthercomprising:

updating, with offset update logic in the text mark, an offset value inthe text mark to identify a position in the node, based on the changeinterpretation.

Example 17 is the method of any or all previous examples and furthercomprising:

updating, using the text mark reference update logic, the one-wayreference to the first change record, in the text mark, to be a one-wayreference to the node.

Example 18 is the method of any or all previous examples and furthercomprising:

allocating memory for the text mark, the node, the first change recordand the subsequent change record; and

releasing memory allocated to any change record which is not referred toby any text mark, change record, or node.

Example 19 is the method of any or all previous examples wherein themethod of processing the content document is performed on a first clientcomputing system and wherein making a modification comprises:

receiving an indication of the modification from a second clientcomputing system; and

identifying the modifications as being made from the second clientcomputing system.

Example 20 is a document processing system, comprising:

a content tree generator that generates a content tree that represents acontent document and has a node;

a content editing system, deployed on a cloud-based client computingsystem, that receives edit inputs through a browser-based interface andmakes a modification to the node, the node including:

a change record generator that generates a first change recordrepresenting the modification to the node; and

a reference update system that updates a reference in the first changerecord to refer to the node and that updates a reference in the node torefer to the first change record; and

a text mark that has a one-way reference to the node, and a positionvalue indicative of a position in the node, and text mark referenceupdate logic that updates the one-way reference to the node to be aone-way reference to the first change record after the first changerecord is generated.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

What is claimed is:
 1. A document processing system comprising: acontent tree generator configured to generate a content tree thatrepresents a content document and has a node; a content editing systemconfigured to make a modification to the node, the node including: achange record generator configured to generate a first change recordrepresenting the modification to the node; and a reference update systemconfigured to update a reference in the first change record to refer tothe node and update a reference in the node to refer to the first changerecord; and a text mark that has a one-way reference to the node, and aposition value indicative of a position in the node, and text markreference update logic configured to update the one-way reference to thenode to be a one-way reference to the first change record after thefirst change record is generated.
 2. The document processing system ofclaim 1 wherein the content editing system is configured to make asubsequent modification to the node, and the change record generator isconfigured to generate a subsequent change record representing thesubsequent modification to the node.
 3. The document processing systemof claim 2 wherein the reference update system in the node is configuredto: generate a reference in the subsequent change record to the node;update the reference in the first change record to be a one-wayreference to the subsequent change record; and generate a reference, inthe node, to the subsequent change record.
 4. The document processingsystem of claim 3 wherein the text mark comprises: a new change recorddetector configured to detect generation of the subsequent changerecord, wherein the text mark reference update logic in the text mark isconfigured to update the one-way reference to the first change record tobe a one-way reference to the subsequent change record.
 5. The documentprocessing system of claim 4 wherein the text mark comprises: changerecord traversal logic configured to traverse the first change recordand the subsequent change record using the one-way reference, in thetext mark, to the first change record, the one-way reference, in thefirst change record, to the subsequent change record, and the reference,in the subsequent change record, to the node.
 6. The document processingsystem of claim 5 wherein the text mark comprises: change interpretationlogic configured to identify the modification and subsequentmodification based on traversal of the first change record and thesubsequent change record and generate a change interpretation based onthe identified modification and subsequent modification.
 7. The documentprocessing system of claim 6 wherein the text mark comprises: offsetupdate logic configured to update the position value in the text mark,identifying the position in the node, based on the changeinterpretation.
 8. The document processing system of claim 7 wherein thetext mark reference update logic is configured to update the one-wayreference to the first change record, in the text mark, to be a one-wayreference to the node.
 9. The document processing system of claim 8 andfurther comprising: a memory management system that allocates memory forthe text mark, the node, the first change record and the subsequentchange record and that releases memory allocated to any change recordwhich is not referred to by any text mark, change record, or node. 10.The document processing system of claim 1 wherein the content editingsystem comprises: a browser-based interface that receives edit userinputs and edits the content document based on the edit user inputs. 11.A method of processing a content document, comprising: receiving acontent tree that represents the content document and has a node; makinga modification to the node; using a change record generator in the nodeto generate a first change record representing the modification to thenode; and using a reference update system in the node to update areference in the first change record to refer to the node and thatupdate a reference in the node to refer to the first change record; andupdating a text mark, that has a one-way reference to the node, and aposition value indicative of a position in the node, by changing theone-way reference to the node to be a one-way reference to the firstchange record.
 12. The method of claim 11 and further comprising: makinga subsequent modification to the node; and generating a subsequentchange record representing the subsequent modification to the node. 13.The method of claim 12 and further comprising, using the referenceupdate system in the node to perform steps of: generating a reference inthe subsequent change record to the node; updating the reference in thefirst change record to be a one-way reference to the subsequent changerecord; and generating a reference, in the node, to the subsequentchange record.
 14. The method of claim 13 and further comprising:detecting, with the text mark, generation of the subsequent changerecord; and updating the one-way reference to the first change record tobe a one-way reference to the subsequent change record.
 15. The methodof claim 14 and further comprising: traversing, with change recordtraversal logic in the text mark, the first change record and thesubsequent change record using the one-way reference, in the text mark,to the first change record, the one-way reference, in the first changerecord, to the subsequent change record, and the reference, in thesubsequent change record, to the node; identifying, with changeinterpretation logic in the text mark, the modification and subsequentmodification based on traversal of the first change record and thesubsequent change record; and generating a change interpretation basedon the identified modification and subsequent modification.
 16. Themethod of claim 15 and further comprising: updating, with offset updatelogic in the text mark, an offset value in the text mark to identify aposition in the node, based on the change interpretation.
 17. The methodof claim 16 and further comprising: updating, using the text markreference update logic, the one-way reference to the first changerecord, in the text mark, to be a one-way reference to the node.
 18. Themethod of claim 17 and further comprising: allocating memory for thetext mark, the node, the first change record and the subsequent changerecord; and releasing memory allocated to any change record which is notreferred to by any text mark, change record, or node.
 19. The method ofclaim 11 wherein the method of processing the content document isperformed on a first client computing system and wherein making amodification comprises: receiving an indication of the modification froma second client computing system; and identifying the modification asbeing made from the second client computing system.
 20. A documentprocessing system comprising: a content tree generator that generates acontent tree that represents a content document and has a node; acontent editing system, deployed on a cloud-based client computingsystem, that receives edit inputs through a browser-based interface andmakes a modification to the node, the node including: a change recordgenerator that generates a first change record representing themodification to the node; and a reference update system that updates areference in the first change record to refer to the node and thatupdates a reference in the node to refer to the first change record; anda text mark that has a one-way reference to the node, and a positionvalue indicative of a position in the node, and text mark referenceupdate logic that updates the one-way reference to the node to be aone-way reference to the first change record after the first changerecord is generated.